End of Roman rule in Britain

The End of Roman rule in Britain was a gradual process which occurred from 383 to 410 AD whereby the Western Roman Empire ultimately decided to evacuate Roman Britain, which had been subjected to various Celtic and Germanic invasions and was tying down large numbers of Roman Army legionaries needed to protect the crumblnig Western Empire's European and North African provinces. The end of Roman rule was quickly followed by the emergence of Romano-British kingdoms and their eventual conquest by the same Germanic mercenaries whom the Romans had imported to fight off the Celts.

Background
By the 360s new challenges were emerging for the Roman rulers of Britain. Picts from beyond Hadrian's Wall became more active and Saxon pirates from northwest Europe started to raid the east coast.

A series of forts was built along the south coast, from the Solent to the Wash, between about 200 and 310 AD. They are known as the Saxon Shore forts, after the Count of the Litus Saxonum (or Saxon Shore), a 5th-century military official who had responsibility for the defense of the region (presumably against the Saxons). What had been one of the more tranquil parts of Britain was now in effect a frontier zone. Some, including Pevensey, were well built and fortified and remained in use by the post-Roman defenderes of Britain against the Saxons. Some were refortified in Norman times. Fourth-century Roman forts in western England, such as at Cardiff and near Lancaster, are an indication that Roman Britain was also being threatened from across the Irish Sea.

History
There are signs that Britain was entering a period of economic decline by the mid-3rd century AD. Industrial activity in towns slackened and high-quality imported pottery disappeared. Elsewhere in the Empire, in northwest Europe, towns were experiencing similar difficulties as the elites tried to escape the onerous duties of being a town councillor (which could be financially ruinous) and retired to their rural villas. Something similar may have occurred in Britain, although even large villas there seem to have suffered economic strains in the 4th century.

Barbarian threats
In 343 AD the Emperor Constans I was forced to visit the province to deal with an unspecified threat, but in 367 a more serious "barbarian conspiracy" broke out in which the Picts are said to have co-ordinated their attacks with the Irish and another group called the Atacotti. The Emperor Valentinian I sent over a senior officer, Count Theodosius, who by 369 had scattered the invaders. He also restored a number of forts along Hadrian's Wall and in the east of England, and added a fifth province (Valentia). In doing so, he established the last brief period of stability Britain would enjoy for centuries.

Withdrawal of troops
Britain's economic difficulties were exacerbated by the steady diminuation of the Roman garrison in the late 4th and early 5th centuries. In 383 a usurper, Magnus Maximus, was proclaimed emperor in Britain. Taking at least a part of the Roman army of Britain, he crossed over to Gaul, where he defeated and killed the official emperor Gratian. Maximus himself ultimately suffered the same fate in 388 and it is likely that a portion of the soldiers he brought from Britain never returned (or were killed in the civil war). It was probably at this time that the Legio XX Valeria Victrix was removed from Chester, leaving the western part of England vulnerable to raiders from across the Irish Sea. The reduction in troop levels appears to have encouraged further barbarian incursions. In 396 Stilicho, the military strongman who dominate the government in the early reign of Honorius (395-423), was forced to come in person to restore order. He did so, but by 4400, he, too, seems to have withdrawn yet more military units from the British provinces. The steady decrease in the numbers of Roman soldiers reduced security and further damaged the economy. Supplies, which had been needed to support the army, were no longer required and the corn to pay its wages stopped being imported. After about 407, bronze coins, which were the only ones really useful for day-to-day transactions, were no longer in circulation in Britain, an indication that the monetary economy had, in effect, collapsed.

The groans of the Britons
The end of Roman rule came with surprising rapidity. In December 406 a horde of barbarians - Alemanni, Vandals, and Burgundii - crossed over the Rhine (which had frozen solid during a harsh winter) and penetrated deep into Gaul. The army in Britain responded by raising another usurper, Marcus, to defend their interests. In rapid succession Marcus was overthrown and replaced by Gratian, who was, in turn, removed by the mutinous troops in favor of Constantine III. An army officer with higher ambitions, he crossed into Gaul with most of the remaining Roman garrison. He was eventually trapped in 411 during a siege of Arles in southern Gaul and executed; his troops never returned to Britain.

Even before this, in 410, however, the Britons are said to have risen up and thrown out all the Roman officials and set up their own rulers. This, however, was probably a revolt against Constantine III's faction rather than a bid for outright independence as they requested help from Emperor Honorius against Saxon raiders from northwest Europe. A letter from Honorius to the British leaders in 411, however, told them that they must look to their own devices and expect no help from Rome. The last mention of contact between Britain and the central Roman authority comes in about 446 when the British leaders addressed a plea to Aetius, the Western Roman Empire's last effective military commander, to "hear the groans of the Britons" and send them assistance against the increasingly predatory Saxon raiders. Aetius had enough problems of his own, however, with Hunnic invaders led by Attila, and the ignored the Britons' plea (if, indeed, he ever received it in the first place).

Aftermath
The period just after the collapse of the Roman province was a confused time, with the arrival of the German barbarians and the emergence of old tribal identieis. After the expulsion of the Roman authorities a number of native kingdoms began to emerge, many of them based on the old pre-Roman tribal centers or civitates. Goods from 5th century graves provide evidence of Anglo-Saxon invaders in Britain. Their culture and traditions are seen in the 10th-century epic poem Beowulf, and bear little resemblance to Roman culture.